Bis-oxazoline compounds have been used as chemical crosslinking agents in various polymer systems. Such compounds are described, for example, in U.S. Pat. No. 6,869,678 (Yamanaka et al.), U.S. Pat. No. 6,753,079 (Husemann et al.), and U.S. Patent Application Publication No. 2010/0137524 (Grittner et al.).
Carboxyl-terminated polymers have been prepared. These are described, for example, in an article of Baumert et al. (Macromol. Rapid Commun., 18, 787-794 (1997)).
Some oxazolinyl-containing polymers have been prepared. For example, WO 96/16999 (Emmerling et al.) describes the preparation of polyurethanes terminated with an oxazolinyl group and JP 2006/124640 (Takako et al.) describes an oxazolinyl-containing acrylic polymer that is crosslinked with a carboxylic acid-containing polymer.
Different methods have been used to reinforce various polymers such as acrylic polymers. For example, crosslinking the polymeric chains can impart greater shear strength and cohesive strength to the materials. This crosslinking can be chemical or physical. Chemical crosslinking can include the introduction of a monomer having at least two groups selected from a polymerizable group capable of undergoing a polymerization reaction and a functional group that are capable of reacting or interacting with other groups within the polymer. Physical crosslinking methods have included the introduction of another polymeric moiety that is linked to the main polymeric component but that has the ability to phase separate from the main polymeric component and form its own domain within the polymeric material. When the polymeric material is an adhesive material, these phase separated polymeric moieties can be selected to have a higher glass transition temperature than the primary viscoelastic polymer as described, for example, in U.S. Pat. No. 6,734,256 (Everaerts et al.), U.S. Pat. No. 7,255,920 (Everaerts et al.), and U.S. Pat. No. 5,057,366 (Husman et al.).